In semiconductor processing, a wafer is cleaned with a chemical to keep the wafer clean. After cleaning, the wafer is treated with a rinsing liquid to remove the chemical from the wafer. After treatment with the rinsing liquid, the wafer is dried to transfer the wafer to a subsequent process.
As a technique of drying a wafer, IPA (Iso-Propyl Alcohol) drying is used. In the IPA drying, a wafer is dried through displacement of a surface of the wafer treated with a rinsing liquid with volatile IPA. However, when the IPA drying is applied to a wafer on which a fine line and space patterns having a width of 20 nanometers or a smaller width are formed, collapse or deformation of the line patterns may occur due to surface tension of the IPA placed between line patterns.
To address this problem, there is a drying technique of using organic sublimable materials in a volatile solvent. In this drying technique, the wafer having the rinsing liquid adhering thereto is coated with the organic sublimable material-containing liquid to displace the rinsing liquid with the organic sublimable material-containing liquid. The volatile solvent in the organic sublimable material-containing liquid is then vaporized, thereby depositing the organic sublimable material on the wafer to embed the organic sublimable material in spaces between the convex patterns. Accordingly, the rinsing liquid having adhered onto the wafer is displaced with an organic sublimable film and is completely removed. A surface of the wafer is dried by sublimating the organic film.
However, in the drying technique using the organic sublimable film, if the volatile solvent vaporizes in a short time, the surface of the organic film is partially undulated and the flatness thereof is degraded. If the flatness of the organic film is degraded, the line patterns still may be deformed or collapsed in an area in which the wafer is not covered with the organic film or an area in which the thickness of the organic film is inappropriate.
Some methods of coating concave and convex patterns formed on a surface of a semiconductor substrate with a resist or an organic silicon material and embedding the resist or the organic silicon material in spaces between the patterns are known. For example, there is a method of coating a semiconductor substrate with a solution containing polysilazane and supplying water vapor or ozone gas to a surface of the substrate to convert polysilazane into a silicon dioxide film. There is also a method of, for example, supplying solvent vapor or applying an ultrasound wave to improve embeddability of a coating film. In this method, structure conversion of the film or concavity improvement of the coating film is achieved by supplying the water vapor or the solvent vapor to the coating film. However, because a domed roof is used for a flat substrate, the vapor supply becomes uneven between a central portion of the flat substrate and an outer circumferential portion thereof. Accordingly, an effect of improving the concavity on the coating film at the outer circumferential portion is likely to reduce.